Water Supply Watershed Classifications

WATER SUPPLY WATERSHED CLASSIFICATIONS

Water Supply I Watersheds

Waters used as sources of water supply for drinking, culinary, or food processing purposes for those
users desiring maximum protection for their water supplies. WS-I waters are those within essentially
natural and undeveloped watersheds with no permitted point source (wastewater) discharges.

WS-I watersheds are entirely composed of publicly owned land and comprise just 0.2% of the total state
land area.

Dischargers: None
Allowable Development: None

Water Supply II Watersheds

Waters used as sources of water supply for drinking, culinary, or food processing purposes for those
users desiring maximum protection for their water supplies where a WS-I classification is not feasible.
WS-II waters are generally located within predominantly undeveloped watersheds.

    WS-II Critical Area

Dischargers: General Permits
Allowable Development:
        Low Density Option: 1du/2ac or 6% built-upon area
        High Density Option*: 6-24% built-upon area
        (* Required to control the 1" storm)
        10/70 Provision: Not allowed
Residuals application: No new sites allowed
Landfills: No new landfills
Agriculture BMPs: Required

    WS-II Balance of Watershed

Dischargers: General Permits
Allowable Development:
        Low Density Option: 1du/ac or 12% built-upon area
        High Density Option*: 12-30% built-upon area
        (* Required to control the 1" storm)
        10/70 Provision: Allowed
Residuals application: Allowed
Landfills: No new discharging
Agriculture BMPs: Not required

Water Supply III Watersheds

Waters used as sources of water supply for drinking, culinary, or food processing purposes for those
users where a more protective WS-I or WS-II classification is not feasible. WS-III waters are generally
located within low to moderately developed watersheds.

    WS-III Critical Area

Dischargers: General Permits
Allowable Development:
        Low Density Option: 1du/ac or 12% built-upon area
        High Density Option*: 12-30% built-upon area
        (* Required to control the 1" storm)
        10/70 Provision: Not allowed
Residuals application: No new sites
Landfills: No new landfills
Agriculture BMPs: Required

    WS-III Balance of Watershed

Dischargers: General Permits; Domestic and Non-process Industrial
Allowable Development:
        Low Density Option: 2du/ac or 24% built-upon area
        High Density Option*: 24-50% built-upon area
        (* Required to control the 1" storm)
        10/70 Provision: Allowed
Residuals application: Allowed
Landfills: No new discharging landfills
Agriculture BMPs: Not required

Water Supply IV Watersheds

Waters used as sources of water supply for drinking, culinary, or food processing purposes for those
users where a WS-I, WS-II, or WS-III classification is not feasible. WS-IV waters are generally located
within moderately to highly developed watersheds.

    WS-IV Critical Area

Dischargers: Domestic and Industrial
Allowable Development:
        Low Density Option: 2du/ac or 24% built-upon area
        High Density Option*: 24-50% built-upon area
        (* Required to control the 1" storm)
        10/70 Provision: Not allowed
Residuals application: No new sites
Landfills: No new landfills
Agriculture Best Management Practices: Required

    WS-IV Protected Area

Dischargers: Domestic and Industrial
Allowable Development:
        Low Density Option: 2du/ac or 24% built-upon area
        High Density Option*: 24-70% built-upon area
        (* Required to control the 1" storm)
        10/70 Provision: Allowed
Residuals application: Allowed
Landfills: Allowed
Agriculture Best Management Practices: Not required

Link to Summary Table of Water Supply Watershed Classifications

Link to Frequently Asked Questions (FAQs)

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